Atherosclerotic cardiovascular disease is the main cause of the long observed early mortality in rheumatoid arthritis (RA) patients. In this project, the possibility that the RA shared epitope (SE) is directly contributing to atherosclerosis development will be explored. The proposed research is based on our recent findings that the SE acts as a ligand capable of activate pro-oxidative signaling in - and secretion of pro-atherogenic factors by - endothelial cells (EC). In prior studies in fibroblasts, the SE-binding molecule has been identified as cell surface calreticulin (CRT), an established innate immunity receptor, whose participation in EC function, immune regulation and autoimmunity has been documented in other systems. It is noteworthy that several known atherosclerosis-modulating proteins, such as C1q, mannose binding lectin and adiponectin, have all been previously shown to transduce signaling via cell surface CRT. We therefore propose that the SE may have a direct pro-atherogenic effect due to aberrant activation of CRT-mediated signaling in EC. As a first step toward examining this hypothesis, an exploratory research project is proposed here with 2 specific aims: 1. To identify key signaling elements in the SE-activated pathway in EC: The general goal of this aim is to better characterize the SE-triggered pro-oxidative pro-atherogenic signaling pathway in EC. Based on published studies in related pathways and our own preliminary data, experiments will be carried out in order to answer the following questions: 1.1) Is CRT the SE-binding receptor in EC?;1.2) Is CD91 acting as a co-receptor in EC?;1.3) What is the role of 2 integrins in SE signaling in EC?;1.4) Does the SE-CRT pathway lead to endothelial 1 nitric oxide (NO) synthase (eNOS) uncoupling? 2. To characterize the atherogenic effects of the SE: We will study the outcomes of SE-EC interaction, focusing on biomarkers, which characterize endothelial dysfunction and AS. To that end, we propose to study the consequences of SE activation of EC: 2.1) in vitro, at the cell culture level;2.2) the effect of these molecules in vivo in SE-positive HLA-DR transgenic mice and;2.3) ex-vivo on tissue samples obtained from these transgenic mice. The studies propose here examine a highly novel hypothesis pertaining to a significant health issue. Successful completion of the proposed studies could shed new light on the role of the immune system in health and diseases and identify novel therapeutic approaches. PUBLIC HEALTH RELEVANCE: Atherosclerosis is a common condition which affects many patients with rheumatoid arthritis and in many cases causes early death. This project will investigate a novel mechanism why patients with rheumatoid arthritis have a higher risk to develop atherosclerosis. The research will focus on the effect of a particular segment of a protein encoded by a gene that is known to be found in higher frequency in patients with rheumatoid arthritis. The ability of that segment to activate blood vessel cells and the biologic effect of that activation will be studied. The results of this study could shed much needed light on a disease that shortens life expectancy of rheumatoid arthritis patients and could identify novel targets for future therapy.